There has been an electrolytic capacitor or an electric double layer capacitor which includes a casing accommodating therein a capacitor element, a seal member configured to seal the casing, and a pressure valve closing a through hole provided to the seal member (see PTL 1). As the pressure valve, a pressure valve 810 having a flat portion 811 as shown in FIG. 11A or a pressure valve 910 having a flat portion 911 as shown in FIG. 11B are used.
When the internal pressure of the casing reaches a certain value, the flat portions 811 and 911 rupture, whereby the gas in the casing is discharged.